In a motorized surgical stapling and cutting instrument it may be useful to control the velocity of a cutting member or to control the articulation velocity of an end effector. Velocity of a displacement member may be determined by measuring elapsed time at predetermined position intervals of the displacement member or measuring the position of the displacement member at predetermined time intervals. The control may be open loop or closed loop. Such measurements may be useful to evaluate tissue conditions such as tissue thickness and adjust the velocity of the cutting member during a firing stroke to account for the tissue conditions. Tissue thickness may be determined by comparing expected velocity of the cutting member to the actual velocity of the cutting member. In some situations, it may be useful to articulate the end effector at a constant articulation velocity. In other situations, it may be useful to drive the end effector at a different articulation velocity than a default articulation velocity at one or more regions within a sweep range of the end effector.
During use of a motorized surgical stapling and cutting instrument the force to fire load on a cutting member or a firing member may vary as a function of tissue thickness. Generally, the force to fire exerted on the cutting member or the firing member will increase as the tissue thickness increases. Therefore, it may be necessary at the initial staging of the cutting member onto a ramp of the closure anvil slot to determine the initial tissue thickness and to set the firing velocity of the cutting member based on the determined tissue thickness to reduce the force to fire load on the cutting member or the firing member. It also may be desirable to provide continuous velocity control of the firing motor based on cutting member stroke over a fixed time interval as a proxy for force to fire load on exerted on the cutting member or the firing member.